Fair exchange ?

Most games of chess will feature exchanges of pieces. Indeed, it is not uncommon for the players to exchange pieces until there is almost nothing left on the board. However, this does not mean it is always good to exchange pieces - sometimes it can be to your advantage to avoid exchanging a particular piece, or to avoid any exchanges at all ... read on

In this game from a Beginner's tournament the first exchange wasn't until the 20th move. After that the contest became one-sided.
* How well did the 4 players use exchanges in the other games ?